Abstract: In order to solve the problem of difficult deformation control in the deep foundation pit project underpassing subway viaduct, this paper relies on the application of pile foundation underpinning technology to pass through an existing subway viaduct project in Beijing, and uses the combination of numerical simulation and field measurement to study the influence of pile foundation underpinning and deep foundation pit construction on the subway viaduct and track structure, and the key parameters are designed. The results show that: The key technologies such as the design value of the jacking force, the optimal pile length, the selection and plane layout of the jacking jack for active underpinning are determined; In the pile foundation underpinning stage, the maximum vertical and transverse deformations of the bridge substructure are 1.620 mm and 1.904 mm, respectively, and the maximum vertical and transverse deformations of the track structure are 1.877 mm and 1.612 mm, respectively. In the foundation pit construction stage, the maximum settlement of the bridge substructure is −2.982 mm, the maximum lateral deformation is 2.530 mm, and the maximum settlement and maximum transverse deformation of the track structure are −2.885 mm, and the maximum transverse deformation is 2.517 mm; The sensitivity of the pier deformation at the adjacent road foundation pit to the change of the parameters of the enclosure structure is as follows: the embedded depth of the enclosure pile > the diameter of the retaining pile > the distance between the retaining piles; The research in this paper can provide a technical reference for the study of the deformation law and control of similar subway bridge structures.